Nature: Particles that are their own antiparticles were predicted by Ettore Majorana in 1937. None have been found in particle-physics experiments so far, but hints of Majorana-like quasiparticles have been seen in a condensed-matter system of strongly interacting electrons. Further, stronger evidence of the quasiparticles comes from a new experiment performed by Ali Yazdani of Princeton University and his colleagues. To create the quasiparticle, they placed a chain of iron atoms on top of a superconductor in such a way that the electrons in the iron atoms paired off. Each pair coordinated spins so that one of the electrons acted like a positron (the antielectron particle). The arrangement left unpaired electrons at both ends of the chain, which forced those two electrons to individually behave as both an electron and a positron. The finding strengthens the idea that true Majorana particles could exist outside of superconductors.
